It is better not to use a modern multigrade in an older design of engine. The additives in modern oils do not suit the older bearing alloys. For an engine which is not doing any work it probably does not matter but if you are thinking of working it then use a straight grade high detergent oil. Shell Rotella 30 was probably one of the best. I use Exol classic HD30 for the Gardners etc which I look after. I can let you have some as I buy it by the 205l drum.Rod